A recent development in the fields of physical therapy and kinesiology has been the concept of "continuous passive motion" ("CPM"). The CPM concept involves the response of the body to gentle, essentially continuous motions induced by sources outside the body. CPM has been particularly significant in the treatment of trauma, where it has been found that the healing process is significantly improved and the recovery period shortened by use of CPM as compared to immobilization. Joint motion is preserved or restored sooner with less tendency for adhesion formation. CPM has also showed marked success in the treatment of muscle spasms and reduction of pain induced by such spasms.
Walking is known to be an effective exercise in many cases for providing motion to the thoracic and lumbar regions of the spine and the pelvis. Walking causes the pelvis to move relative to the lower back and can alleviate the symptoms of lower back muscles spasms. It is also an excellent exercise for healthy individuals, in that the walking keeps the spinal joints limber and helps prevent the onset of lower back problems Keeping the joints in good condition through walking can also lessen the severity of damage if the lower back is subsequently subjected to trauma.
Unfortunately, many people's occupations require them to remain seated or standing for extended time periods at a desk, work station, etc. Their opportunities to walk are therefore limited Other people are bed-ridden because of injury, illness or other infirmity and are unable to walk. These prolonged periods of sitting or reclining do not permit effective motion of the lower back, so that existing pain may persist or reduced joint and muscle mobility may develop.
The analogies between CPM and walking are evident. Light to moderate walking induces a gentle continuous motion to the lower back and pelvis. Its effects on speeding recovery from trauma are reflected in the wide-spread prescribing of walking by doctors for injured patients and also in the almost universal practice in hospitals of encouraging surgical patients to walk as soon as possible, sometimes within hours, after their surgery.
Other portions of the spine benefit from CPM. Motion of the neck is effective in reducing or eliminating pain from spasms in the neck muscles and cervical spine or to prevent the muscle and joint stiffness that a person often suffers upon awakening after a night's sleep when the head is kept in the same position for a long period. Similarly, motion of the mid body alleviates stiffness in the lumbar and thoracic spine caused by maintaining the body in a supine position, as during bed rest. While everyday activities usually provide sufficient motion to these parts of the body to avoid such pain, bed rest, sleeping or other factors may act to prevent a person from actively moving the affected parts of the spine and associated muscles.
It would therefore be advantageous to have a device which would allow users to obtain many of the beneficial effects of CPM for application to the spine and associated muscles, including the pelvis and neck, when such users cannot actually engage in the required amount of walking or other activities to provide the desired motions.
In the past devices have been described in which air cells have been sequentially inflated and deflated to support or apply pressure to portions of the body, notably the back and legs. Such devices have had two major deficiencies: they did not simulate normal body motions, but merely applied mechanical pressure to different body areas, and they operate unidirectionally, causing unidimensional movement only in the sagittal plane. Typical of the prior art devices are those shown in U.S. Pat. Nos. 2,719,986; 3,613,617; 3,653,083; 4,068,334; 4,197,837 and 4,396,010.